1. Field of the Invention
The present invention relates to conveyor belts having a drive mechanism, such as belts that travel on a straight path, around turns or on along a helical track, and specifically concerns the conveyor rods and side link connections in such conveyor belts.
2. Description of the Related Art
It is known to use a conveyor belt in high volume production operations performed in a relatively small space where the conveyor belt moves in an upward or downward spiral path. It is also known that certain of such conveyor belts include a plurality of interconnected pivotal link members which allow the belt to follow a curved path or traverse a sprocket in either an upward or downward direction when following the straight-line path; and a plurality of transverse rod members of an overlying belt tier, the rod members having ends with enlarged heads. Additionally, it is known to secure said link members to the transverse rod members by passing the rod through the link member and fastening the enlarged head of the rod member to the outside of the link member such that the rod head protrudes outside of the link.
A known conveyor system of this type is disclosed in U.S. Pat. No. 3,348,659 to Roinestad. In this system the belt is frictionally driven along the inside edge by an upright drum with a peripheral driving surface. A series of vertical driving bars are positioned around the periphery of the drum at circumferentially spaced locations and engage in a frictional driving relationship with the inner edge of the belt. The belt may comprise a plurality of transverse rods which interconnect a plurality of a U-shaped link members wherein such link members slidably nest within each other and enable the belt to be collapsed along either edge. The link members are slotted to receive the rods. At the extreme outer edge of each of the rods outside of the link members, there is an arcuate dome-shaped protrusion which may be formed by a welding operation to secure the ends of the rods with respect to the link members. In this system, the head of the rod extends through the link and is welded to the outside of one end of the link. It is the frictional driving engagement between the vertical driving bars and the arcuate protrusions which provide the primary drive for the belt.
Another known conveyor system is described in U.S. Pat. No. 5,350,056 to Hager. In this system, the conveyor belt is self-supporting with a portion of the belt following a helical conveying path comprising a plurality of stacked tiers. The belt includes a plurality of interconnected pivotal link members by which the belt can either collapse or extend along a side edge thereof to follow a curved path; and a plurality of transverse rod members of an overlying belt tier. Secured to the link members are wire formed spacers which extend between adjacent belt tiers. One embodiment of the system includes rods formed with an enlarged head which are received through slots in the link members and secured to the outside of the end of the link member by, e.g., welding, so that the rod heads protrude on the outside of the ends of the link members.
One method of securing the transverse rods with enlarged heads to the link members is by buttonhead or upset welding the head to the outside of one end of the link member. In this type of welding, the buttonhead weld is cold formed and then a plasma type weld affixes the rod to the outside of the link.
Although the self-supporting spiral conveyor belt disclosed in the 5,350,056 patent represents a significant advance in the art, there remains room in the art for improvement, particularly with respect to the manner in which the rods are secured to the link members, wherein the rod heads protrude and are welded to the outside of one end of the link members. One of the areas for improvement arises because the conventional buttonhead type welding can result in a driven surface that will, over time, abrade the portions of the drive mechanism which engages the belt; if such portions of the drive mechanism are plastic, such abrasion can cause plastic fires that contaminate the portions. This is because current systems which use buttonwelded links with welds can develop burrs or uneven projections on the edge of the belt that engages the driving mechanism.
Further, welding the links to the connecting rod under current designs requires considerable care because the weld on the outside of the link, e.g., the plasma weld, must be accurately placed, of sufficient size/cross-section, but yet it must not extend out past the buttonhead weld. The outside edge of the belt should be uniform, and free of sharp or uneven projections or else it could create drive problems between the belt edge and the portion of the drive mechanism that engages the belt. Thus, it is desirable to obtain a sufficiently strong weld without interfering with the extreme outside edge of the belt. Also, buttonhead type welding is a relatively expensive operation and inserts extra steps into the production process.
Accordingly, there is a need in the art for a conveyor belt which improves upon current conveyor belt designs.